ok, i'll cover a few things here:

1. You don't need speakers in the back, save your money and purchase a set of decent splits for up front. get some ones that sound great to you, who cares what other people think? if you go out and buy a set that is apparently good, you could put them in your car, and find they sound like arse to you. As trism said, at a concert, sounds come from infront of you, not behind.

2. if you get a headunit, you'll want something with 2rca's (sub out/ rear out left and right, front out left and right) so you can run the monoblock and 2 channel.

3. If you so desperately want rears, keep the stock ones and run them off the headunit. you'll get your rear fill, and it'll be cheaper.

4. To be safe, it's a good idea to get something around this:
6 meters 4awg minimum for power (by minimum, I mean 4awg minimum. I'd probably opt for 2awg myself, just to be safe, but 4awg will suffice)
1 meter of same awg as power, so if you go 4awg power, get 1 meter of 4awg for ground.
6 meters of 16awg i think it is remote wire
2 rca's
10 meters 12awg speaker wire for speakers. (that should be enough to get from front doors to boot and sub to monoblock.
at least 4 meters of same sized wire as power wire for big 3 upgrade. so at least 4 meters of 4awg. can use 0awg if you want, up to you really.

5. you sound like you're going off maximum power for a lot of things, always go off rms, as rms is pretty much the actual power.

6. Power on an amp is not like a light switch, it can be turned up and down. if the amp runs 100wrms x 2 it doesn't mean your speakers will get 100wrms in them. same with your monoblock, if you turn the gains down, you won't overpower them